Method of forming low-k films

ABSTRACT

To deposit silicon carbide into a substrate, there is introduced into a reaction zone a gas including source gas of silicon, carbon, oxygen and an inert gas. An electric field is generated using low and high frequency RF power to produce a plasma discharge in the reaction zone to cause the deposition.

FIELD OF THE INVENTION

The present invention relates to oxygen doped silicon carbide layersreferred to herein as SiCO and, more particularly to a method of forminglow dielectric constant, low leakage current with high elastic modulusand hardness oxygen doped silicon carbide layers.

BACKGROUND OF THE INVENTION

Integrated circuits have evolved into complex devices that includemultiple levels of metal layers to electrically interconnect discretelayers of semiconductor devices on a single semiconductor chip.Recently, with the evolution of higher integration and higher density ofintegrated circuit components, the demand for greater speed of the datatransfer rate is required. For this reason, an insulating film havinglow leakage current, low dielectric constant with high elastic modulusand hardness, to give the small RC delay is employed.

As the device dimensions continuously shrink, the RC time delay of theinterconnect system becomes one of the most important limitation factorsto the integrated circuits performance. The RC delay is directlyproportional to the resistivity of the metal and the dielectric constantof the dielectric. In order to minimize the signal propagation delay, itis inevitable to use low dielectric constant materials as theinter-layer and intra-layer dielectrics (ILD).

The initial approach for providing low-dielectric films was the dopingof the silicon oxide material with the other components such as fluorinethat reduces the dielectric constant but only to that of about 3.5 to3.9. Since the fluorine doped silicon oxide films offer only a smalldecrease in the dielectric constant, other solutions having lowerdielectric constant are required. Furthermore, the stability of thefluorine doped silicon oxygen films with regard to moisture isproblematic.

In an approach for providing a silicon oxide layer having a planarsurface, spin-on-glass composition have been prepared utilizingpolyorganosilsesquioxanes as presented in U.S. Pat. No. 4,670,299. Theadvantages of this film is that it has low dielectric constant such asthat of 2.6 to 3.0, and also maintain the higher mechanical strengths ofsilicon oxide type films.

However, it would be advantageous to have a final dielectric film thatcombines the advantage of a film formed from organic polysilicas such aspolyorgansilsesquioxanes referred to herein as POQS with an even lowerdielectric constant (k<2.5). The most likely method for achieving thisresult is to blend the POSQ with another substance with lower dielectricconstant. A substance with lower dielectric constant is air (k=1). So,in order to achieve lower dielectric constants, porosity needs to beintroduced into the POSQ material. However, the process of introducingporosity is complex and is slow.

Furthermore, to reduce the size of interconnection lines and vias is tochange the wiring materials from the conventional aluminum (Al) tocopper (Cu) wiring having low electric resistance. However, to produce asemiconductor device having multi-layered copper wiring, a lowdielectric constant insulating layer is formed as the interlayerinsulating film on the copper wiring.

The use of copper as the interconnect material has various problems. Forexample, copper is easily diffused into the low dielectric constantinsulating film from the copper wiring, thus increasing the leakagecurrent between the upper and lower wiring.

The use of silicon carbide films as copper diffusion barrier layers hasbeen published in U.S. Pat. No. 5,800,878. The dielectric constant ofthis film is about 5, and in addition it is used as copper diffusionbarrier layers for 130 nm-nodes Large Scale Integration (LSI)technologies where the dielectric constant of the interlayer dielectricfilm is 3.

For next generation, 100 nm/65 nm-nodes Ultra Large Scale Integration(ULSI) technologies, the reduction of interconnect capacitance isimportant for suppressing the signal delay as well as the powerconsumption. Interlayer dielectric films with dielectric constant lessthan 2.5 are used with copper damascene structures. To decrease theeffective dielectric of fine pitched lines, further reduction in thedielectric constant is necessary not only for the inter layer dielectricfilm itself but also the supporting dielectric films such as hard mask,etch stop layers and copper diffusion barrier layers. However, theprocess is difficult.

The interface between copper and copper diffusion barrier layer is knownto be the key point for the electro-migration reliability of copperinterconnects. The interface between copper and the copper diffusionbarrier layer is the dominant diffusion path. However, there is noreport on the identification of the dominant path for copperinterconnects. On the other hand, the interface can be not only thedominant path but also the electro-migration induced void nucleationsite.

The strength of adhesion between copper and diffusion layer would affectthe electro-migration induced void nucleation because electro-migrationinduced void nucleates when copper atom at the interface is strippedaway from the diffusion layer. It is also suggested that in order toprevent the migration of metal atoms, the film has to have a stable filmstress even after being directly exposed to air at room temperature ofabout 20 to 30° C. Furthermore, the leakage current and dielectricconstant of such film at 1 MV/cm has to be less than that of 1×10⁻⁹A/cm² and less than 3.5 respectively. SiCO films with dielectricconstant less than 3.5 such that the leakage current at 1 MV/cm is lessthan 1×10⁻⁹ A/cm² are suggested to be suitable to substitute for suchfilms.

Using the silicon carbide film as an etch stop film was developed andpresented in U.S. Pat. No. 5,800,878. A dielectric constant of thesilicon carbide film is approximately 5. Silicon carbide films areapplied to LSI devices using copper wiring in combination withcarbon-containing silicon oxide films, whose dielectric constant isapproximately 3. There are several different types of compositions forwhat is generally called silicon carbide films. One type is a siliconcarbide film comprising Si, C and H. This film's stress and dielectricconstant changes if left in the atmosphere. This is due to the oxidationof the top surface of the silicon carbide film. The method to minimizethe oxidation of carbon containing materials, such as silicon carbide,with an inert gas plasma such as helium (He), Argon (Ar) is published inJP laid-open patent 2001/0060584. This inert gas plasma treatment onlyminimizes the top surface of the silicon carbide film from gettingoxidized, however, no changes/improvements to the film properties areobserved.

The method of forming nitrogen doped silicon carbide (SiCN), oxygendoped silicon carbides (SiCO) has been published in United States PatentApplication Publication 2001/0030369, United States Patent ApplicationPublication 2002/0027286, United States Patent Application Publication2001/0051445, and United States Patent Application Publication2001/0031563. Furthermore, these films have been proposed as copperdiffusion barrier layers. Though a nitrogen doped silicon carbide layerhas been proposed as a copper diffusion barrier layer with low leakagecurrent, its dielectric constant is high such as 5.

Therefore, there is a need for a low dielectric constant film which alsosupports the copper diffusion barrier layers properties and is usefulfor the fabrication of IC devices, where the film is mechanicallystrong, useful at high temperatures, and is easily and quicklyfabricated.

SUMMARY OF THE INVENTION

Thus, it is desired to develop a new method of forming low dielectricconstant layers supporting copper diffusion barrier layers propertiesthat can be employed in the next generation, 100 nm/65 nm-nodes UltraLarge Scale Integration (ULSI) technologies, where the copper damascenestructures are used.

The main characteristics of low-k dielectric layer and copper diffusionbarrier layers such as oxygen doped silicon carbide films (SiCO)developed using various embodiments of the present invention are asfollows:

-   a) The dielectric constant is less than 3.0-   b) No changes to its film properties such as changes to the film    stress or changes to film dielectric constant are observed even when    directly exposed to air at a room temperature between 20° C. to 30°    C.-   c) The leakage current at 1 MV/cm is extremely low, such as less    than 5×10⁻⁹ A/cm².-   d) The elastic modulus and hardness are above 10G Pa and 2G Pa    respectively.

According to one preferred embodiment of the present invention, a methodof forming low dielectric constant, low leakage current with highElastic modulus and Hardness silicon carbide film for use in integratedcircuit fabrication processes is provided. The silicon carbide film isdeposited on a substrate by introducing alkyl silicon compounds such asdivinyl-dimethylsilane (Si(CH═CH₂)₂(CH₃)₂), tri-methylsilane (SiH(CH₃)₃)or tetra-methylsilane (Si(CH₃)₄) referred to herein as TMS, asubstantial source of oxygen such as oxygen (O2) or carbon dioxide (CO2)and an inert gas such as argon (Ar), helium (He), krypton (Kr), neon(Ne) or xenon (Xe) in the presence of an electric field in a plasma CVDreactor.

A mixture of high and low frequency RF power, such that high frequencyRF power is in the range of 13.56 MHz to 30 MHz and low frequency RFpower is in the range of 200 kHz to 500 kHz, wherein the ratio of lowfrequency to total power is less than about 0.5, generates the electricfield. The leakage current and dielectric constant of the siliconcarbide in this invention is decreased by introducing excess amount ofoxygen and inert gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an exemplary plasmachemical vapor deposition device.

FIGS. 2 a-2 j illustrate a dual damascene structure in which a siliconcarbide layer can be used.

FIG. 3 illustrates an exemplary sequence (deposition recipe) for forminga SiCO film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Disclosed herein is a method for depositing a silicon carbide filmhaving a low dielectric constant, low leakage current, high elasticmodulus and high hardness onto a substrate in a CVD chamber, comprisingthe steps of providing a silicon source, carbon source, oxygen sourceand an inert gas in a reaction zone containing a substrate, and reactingthe silicon and carbon and oxygen source in the presence of a plasma todeposit a low dielectric constant and low leakage current siliconcarbide film on the substrate.

A mixture of high and low frequency RF power generates the electricfield, wherein the ratio of low frequency to total power is less thanabout 0.5. The leakage current and dielectric constant in the resultingsilicon carbide film is directly related to the carbon concentration,amount of oxygen and inert gas introduced.

Silicon Carbide Layer Formation

In one preferred embodiment of the present invention, a silicon carbidelayer is formed by reacting a gas mixture including, silicon source,carbon source, oxygen source and an inert gas into a plasma enhancedchemical vapor deposition (PECVD) chamber. Details of the processingsystem are illustrated in FIG. 1.

FIG. 1 is a schematic cross section of an exemplary plasma CVD deviceaccording to a preferred embodiment. A plasma CVD device 1, which isused to form a thin film on a semiconductor wafer 9 or other substrate,comprises a reaction chamber 2, a support 3 provided within the reactionchamber to support the semiconductor wafer 9, a shower-head 4 that ispositioned to face the support 3 and is used to spray reaction gasuniformly onto the semiconductor wafer 9, an outlet 20 to exhaustreaction gases and byproducts from the reaction chamber 2, and a remoteplasma chamber 17. Cleaning gas for the remote plasma chamber 17 issupplied through a conduit 18 having an inlet port 16 leading to a mainflow controller 14 and a valve 15. The remote plasma discharge chamber17 is linked to the showerhead 4 via piping 6 and valve 7. The remoteplasma discharge chamber 17 generates active species usingradio-frequency oscillating output energy of the designated frequency,and the piping 6 is made of materials that are not corroded by theactive species.

The support 3 that is provided within the reaction chamber 2 and that isused to support the semiconductor wafer 9 is made of anodized aluminumalloy and is grounded 27 to constitute one side of an electrode ofplasma discharge. The reaction chamber 2 of the illustrated embodimentis thus a plasma CVD chamber configured for in situ (in chamber) plasmageneration. The support 3 includes a heater 5 having a ring-shapeheating element 24 embedded therein. The semiconductor wafer'stemperature is controlled at a predetermined temperature using atemperature controller (not shown). The support 3 is connected to adriving mechanism 26 that moves the support 3 up and down through asupport piston 25.

Within the reaction chamber 2, the showerhead 4 is provided at aposition facing the support 3. In the showerhead 4, thousands of fineholes are provided to inject reaction gas onto the semiconductor wafer9. The showerhead is electrically connected to a radio-frequencyoscillator 8 and 8′ via matching circuit 10 and constitutes anotherelectrode for plasma discharge. To bring reaction gas to be used forfilm formation from the showerhead 4, a reaction gas conduit 12 isconnected to a mass flow controller 14 with a shut-off valve 15 near theoutlet from the flow controller and a valve 11 controlling flow to thepiping 6. The number of the gas conduits is not limited to one.According to the type of reaction gas, any number of gas conduits can beinstalled. One end of the gas conduit 12 constitutes a gas inlet port 13to cause reaction gas to flow in and the other end constitutes areaction gas exit port to cause gas to flow to the inlet 29 of theshowerhead 4.

The outlet 20 is connected to a vacuum pump (not shown) through piping19. Between the outlet 20 and the vacuum pump, a conductance-controllingvalve 21 is provided to regulate pressure within the reaction chamber 2.The conductance-controlling valve 21 is electrically connected to anexternal regulator 22 and a pressure gauge 23, preferably provided tomeasure pressure within the reaction chamber 2. The wafer 9 is insertedinto the chamber 2 through a port 28 controlled by a gate valve 30.

The silicon and carbon source may be an alkyl silicon compound having ageneral formula Si_(x)C_(y)H_(z), where x has a range from 1 to 2, y hasa range from 1 to 6, and z has a range from 6 to 20. For example,divinyl-dimethylsilane, tri-methylsilane, and tetra-methylsilane amongothers maybe used as the alkyl silicon compound. Oxygen source is oxygen(O2) and carbon dioxide (CO2). Helium (He), argon (Ar), neon (Ne),krypton (Kr) and xenon (Xe) maybe used for the inert gas.

In general, the deposition process parameters of forming a siliconcarbide film on a 200 mm silicon wafer include a substrate temperaturerange of about 200° C. to about 400° C. (more preferably 300-350° C.), achamber pressure of about 300 Pa to 1000 Pa, an alkyl silicon compoundflow rate of about 100 sccm to 1000 sccm, oxygen source flow rate suchas oxygen (O2) of about 10 sccm to 500 sccm, and an inert gas flow rateof about 200 sccm to 5000 sccm. This creates a ratio of the inert gasflow rate to alkyl silicon compound is in the range of about 1:1 toabout 1:10. The process also includes a mixed frequency RF power havingat least a first RF power with a frequency in a range of about 13 MHz to30 MHz (high frequency) with a power in a range of about 100 Watts to2000 Watts; and at least a second RF power with a frequency in a rangeof about 100 kHz to 500 kHz (low frequency) with a power in the range ofabout 10 Watts to 500 Watts. Thus the ratio of low frequency to totalpower is less than about 0.5, and the RF power source generates theelectric field. Preferably the first RF power is in the range of 100to1000 W and the second RF power is in the range of 10 to 250W. The secondRF power with a frequency in a range of 300 kHz to 450 kHz is preferablyused in combination with the first RF power.

The ratio of the second RF power to the total mixed frequency power ispreferably less than about 0.5 to 1.0. The above process parametersprovide a deposition rate for the silicon carbide layer in the range ofabout 0.2 μ m/min to 1 μ m/min, when implemented on a 200 mm substratein a deposition chamber.

The details on film forming steps and parameters are explained below.

Silicon Carbide Film Formation

As an exemplary process for growing silicon carbide film on a substrateaccording to the present invention, the parameters listed in TABLES 1through 3 were used: TABLE 1 Range Parameter Step 1 Step 2Tetra-methylsilane (TMS) flow rate 100 sccm˜1000 sccm 0 sccm˜500 sccmHelium (He) flow rate 100 sccm˜10000 sccm 100 sccm˜10000 sccm Oxygen(O2) flow rate 10 sccm˜5000 sccm 0 sccm˜1000 sccm Pressure 300 Pa˜1000Pa 300 Pa˜1000 Pa Primary RF Power 100 W˜2000 W 100 W˜2000 W SecondaryRF Power 10 W˜500 W 10 W˜500 W Substrate Temperature 200° C.˜400° C.200° C.˜400° C.

TABLE 2 Preferred Range Parameter Step 1 Step 2 Tetra-methylsilane (TMS)flow rate 100 sccm˜700 sccm 0 sccm˜300 sccm Helium (He) flow rate 100sccm˜3000 sccm 100 sccm˜5000 sccm Oxygen (O2) flow rate 20 sccm˜1000sccm 0 sccm˜500 sccm Pressure 300 Pa˜1000 Pa 300 Pa˜1000 Pa Primary RFPower 100 W˜1000 W 100 W˜1000 W Secondary RF Power 20 W˜300 W 20 W˜300 WSubstrate Temperature 250° C.˜350° C. 250° C.˜350° C.

TABLE 3 More Preferred Range Parameter Step 1 Step 2 Tetra-methylsilane(TMS) flow rate 100 sccm˜500 sccm 0 sccm˜100 sccm Helium (He) flow rate100 sccm˜1000 sccm 100 sccm˜2500 sccm Oxygen (O2) flow rate 20 sccm˜500sccm 0 sccm˜250 sccm Pressure 300 Pa˜800 Pa 300 Pa˜800 Pa Primary RFPower 350 W˜500 W 350 W˜500 W Secondary RF Power 50 W˜150 W 50 W˜150 WSubstrate Temperature 300° C.˜350° C. 300° C.˜350 ° C.

Silicon Carbide Film Forming Conditions/Sequence

To deposit silicon carbide layer on 200 mm wafer, a reactive gas sourcesuch as tetra-methylsilane (TMS) is introduced into the reaction zone.Oxygen is used as an oxygen source. Helium is used as an inert gas. SeeTABLES 1 through 3 for gas flow rates. The chamber is maintainedpreferably at about 300 to 1000 Pa, more preferably maintained at about300 Pa to 800 Pa. A mixed frequency of 27.12 MHz and 400 kHz RF powersource preferably delivers at least about 100 Watts to 2000 Watts and atleast about 10 Watts to 500 Watts respectively. More preferably 27.12MHz RF power of 400 W and 4000 kHz RF power of 100 W is applied forforming films.

Silicon carbide film deposition steps are divided into 2 steps. First,basic film is formed on the substrate by flowing TMS, O2, He andapplying RF power as shown in FIG. 3 (TMS=300 sccm; O2=100 sccm; He=400sccm; 27.12 MHz at 400W; 400 kHz at 100W; substrate temperature=340° C.;chamber pressure=733 Pa).

Second, an active plasma treatment step is performed. After the basicfilm formation step, second film formation is carried out continuously.In this step, Helium flow is increased while TMS and O2 flow isdecreased without changing plasma discharge. One has to consider thatthe film formation is continued during the active plasma treatment(TMS=Ramp down to 0 sccm; O2=Ramp down to 0 sccm; He=Ramp up to 2.5 slm;27.12 MHz at 400W; 400 kHz at 100W; substrate temperature=340° C.;chamber pressure=733 Pa).

The basic film properties of the silicon carbide film deposited usingthe above steps and conditions are shown in TABLE 4.

A silicon carbide film deposited by the basic film forming step alone isnot stable, its film stress and dielectric constant changes when exposedto air at room temperature. This is due to the oxidation of the surfacelayer. The method of minimizing the oxidation of carbon containingfilms, such as SiC is published in United States Patent ApplicationPublication 2002/054962; however, no changes/improvements to the filmproperties are observed. Furthermore, when annealing is performed at400° C. under nitrogen atmosphere for 10 hours, a drastic change in thefilm stress is observed. The change in the stress is about 400 MPa,which consequently implies to a poor thermal stress stability behavior.

When an active plasma treatment in this invention is performed on thesilicon carbide films, the unstable phenomena of the film stress anddielectric constant are solved. Also the dielectric constant and leakagecurrent is decreased. Furthermore, after annealing at 400° C. undernitrogen atmosphere for 10 hours, almost no changes to the filmproperties are observed. It is presumed that the silicon carbide filmdeposited according to the embodiments described above has a goodthermal stress behavior.

The silicon carbide films deposited by the PECVD process describedherein have significantly lower dielectric constant and lower leakagecurrent in comparison to the conventional silicon carbide films.Furthermore, the silicon carbide film deposited according to the asdescribed above has a mechanical properties such as high elastic modulusand high hardness. The silicon carbide films can be deposited without amixture of low and high frequency. However, the preferred mixture ofhigh and low radio frequency corrects adverse film properties caused bythe bombardment of the silicon carbide film with molecules of inert gas.Increasing the ratio of Si—C bonds in the film provides greater hardnessand high elastic modulus in the silicon carbide film.

The following example illustrates a dual damascene structure in which asilicon carbide layer deposited according to the present invention canbe used. FIGS. 2 a-2 j show a dual damascene structure in which asilicon carbide layer deposited according to the present invention canbe used. A copper (Cu) layer (31) is first covered with a siliconcarbide layer (32). Since the silicon carbide layer (32) according tothis embodiment has low oxygen content with low leakage current, lowdielectric constant with high elastic modulus and high hardness, it issuggested to be the most suitable material to use as a copper diffusionbarrier layer. Before depositing the silicon carbide layer (32), thecopper surface can be improved by removing any copper oxide that may beremaining on the surface. Typically a hydrogen (H₂) or an ammonia (NH₃)or methane (CH₄) plasma based reduction is used before the deposition ofsilicon carbide layer (32). This copper surface reduction to remove CMPresidue can be performed in a PECVD chamber.

After the deposition of silicon carbide layer (32), a photo resist (33)is coated as shown in FIG. 2 b. To form via holes and trenches, anysuitable methods can be employed. The following is an example:

A via hole (35) is formed by etching. The process of forming a via holeis stated as follows: First a photo resist (33) is removed (34) as shownin FIG. 2 c. Next, a via etching is commenced through the siliconcarbide layer (32) as shown in FIG. 2 d. Finally, The silicon carbidebreakthrough step is performed to expose the underlying copper layer.

After via realization, trench patterning commences. After via etch andcleans are performed as shown in FIG. 2 e, the wafer is coated withSacrificial Light Absorbing Material (SLAM) and patterned with trenchphoto resist (not shown). Post trench etch, SLAM remains at the bottomof the vias and on top of the wafer (not shown). SLAM is removed fromeverywhere on the wafers with high selectivity to the silicon carbideduring the trench etch clean step as shown in FIG. 2 f.

A copper barrier layer such as TaN or TiN (37), is formed inside the viahole as shown in FIG. 2 g. A copper seed layer (38) is further depositedby PVD, or the like. Thereafter copper (39) is then deposited in thehole (36) by electric plating or the like. By CMP or the like, copperbarrier layer (37), copper (38), resist (33), and sacrificial amount ofsilicon carbide layer are removed so that the surface (40) is exposed. Asilicon carbide layer can also be deposited as a passivation layer (notshown) for protecting the device from scratching.

The dielectric constant and leakage current at 1 MV/cm of conventionalsilicon carbide barrier layer is approximately 5 and 5×10⁻⁷ A/cm² whencompared to that of approximately 2.8 and 5×10⁻¹⁰ A/cm² respectively ina silicon carbide barrier layer fabricated as described herein.

Furthermore, silicon carbide film according to the present invention ismechanically strong such as has high elastic modulus and hardness ofapproximately >10 G Pa and >2 G Pa respectively when compared to theother low-k films typically made of, for example inorganic materialssuch as fluorosilicate (FSG), hydrogen silsesquioxane (HSQ), methylsilsesquioxane (MSQ), and others like the same.

The advantage of the present invention is that this silicon carbidelayer has improved electrical properties, including: (1) a higherbreakdown voltage, (2) lower leakage currents, and (3) both greater filmstability, and improved mechanical properties in terms of hardness.Moreover, the silicon carbide according to this present inventiondisplays a dielectric constant that is less than 3.0, which improves theelectrical performance of devices.

Thus, using a conventional silicon carbide barrier layer, as opposed toa silicon carbide layer fabricated as described herein, at an electricfield of 2 MV/cm, maintains the same effectiveness in preventing thecopper diffusion. Furthermore, the resulting silicon carbide layer has arelatively low dielectric constant, typically around less than 3.0,depending on the mixture and ratio of low frequency to the totalfrequency generated during deposition, and also depending on the ratioof gases used to form the silicon carbide.

The film formation was conducted according the deposition conditionsshown in Table 4 below. TABLE 4 Parameter Step 1 Step 2Tetra-methylsilane (TMS) flow rate 300 Ramp down to 0 sccm (sccm) Helium(He) flow rate (sccm) 400 Ramp up to 2500 sccm Oxygen (O2) (sccm) 100Ramp down to 0 sccm Pressure (Pa) 733 733 Low RF Power (W) 100 100 HighRF Power (W) 400 400 Substrate Temperature (° C.) 340 340

An as-deposited silicon carbide layer has a dielectric constant andleakage current at 1 MV/cm less than about 3.0 and 5×10⁻¹⁰ A/cm²,respectively, making it suitable for use as an insulating material inintegrated circuits. The details of the film properties such asdielectric constant, leakage current and film stress of the siliconcarbide layer deposited according to the deposition conditions shown inTable 5. The dielectric constant of the silicon carbide layer istunable, in that it can be varied as a function of the ratio of themixed frequency RF powers. In particular, as the ratio of the lowfrequency RF power to the total mixed powers decreases, the dielectricconstant of the silicon carbide layer also decreases.

The dielectric constant of the silicon carbide layer can also be tunedas a function of the composition of the gas mixture during layerformation. As the carbon concentration in the gas mixture increases, thecarbon content of the as-deposited silicon carbide layer increases,making the silicon carbide film less dense and dielectric constantdecrease. Also, as the carbon concentration of the as deposited siliconcarbide layer increases, the hydrophobic properties thereof increasesmaking such layers suitable for use as moisture barriers in integratedcircuits.

In addition, the as-deposited silicon carbide layer has low oxygencontent. Thermal anneal test was used to check the barrier capability ofthe silicon carbide layer. Thermal penetration of the copper atom intothe silicon carbide film was measured by secondary ion mass spectroscopy(SIMS). The copper penetration depth of the silicon carbide layer wasless than 18 nm that indicates that the thermal diffusion of copper canbe blocked effectively. It indicates that such a low oxygen contentsilicon carbide layer minimizes metal diffusion and improves the barrierlayer properties. For example, the as-deposited silicon carbide layerhas a current blocking ability at 1 MV/cm that is less than that about1×10⁻⁸ A/cm², which is suitable for minimizing cross-talk betweenintegrated circuit interconnect structures. TABLE 5 Dielectric Leakagecurrent at Elastic Film type constant 1 MV/cm Modulus Hardness SiCO 2.8± 0.1 <5 × 10⁻¹⁰ 15 GPa 2.2 GPa

1. (canceled)
 2. The method of claim 34, wherein: the high frequency RFpower has a frequency between about 13 MHz and about 30 MHz, and has apower between about 200 watts and about 1000 watts; and the lowfrequency RF power has a frequency between about 100 kHz and about 500kHz, and has a power between about 50 watts and 500 watts.
 3. The methodof claim 34, wherein a ratio of the low frequency RF power to a total RFpower is less than about 0.5.
 4. The method of claim 34, wherein theaverage power at the electrode surface is substantially constant.
 5. Themethod of claim 34, wherein the silicon and carbon source gas is one ofthe following: tri-methylsilane, tetra-methylsilane, ordivinyl-dimethylsilane.
 6. The method of claim 34, wherein the inert gasis one of the following: helium, argon or krypton.
 7. The method ofclaim 34, wherein the oxygen source in either one of the following orboth: Oxygen (O2) or Carbon dioxide (CO2).
 8. The method of claim 34,wherein the ratio of the silicon and carbon source gas to the inert gasis between about 1:1 and about 1:15.
 9. The method of claim 34, whereinthe silicon and carbon source gas is provided into the reaction zone ata rate between about 200 sccm and about 500 sccm.
 10. The method ofclaim 34, wherein the substrate is heated to a temperature between about200° C. and about 400° C.
 11. The method of claim 10, wherein thesubstrate is heated to a temperature between about 320° C. and about350° C.
 12. The method of claim 34, wherein the reaction zone ismaintained at a pressure between about 300 Pa and about 1000 Pa.
 13. Themethod of claim 34, wherein the reaction zone is maintained at apressure between about 500 Pa and about 800 Pa.
 14. The method of claim34, wherein the silicon source and the carbon source are TMS, the oxygensource is O2, and the inert gas is He
 15. The method of claim 14, wherethe film formation is continued during the active plasma treatment step.16. The method of claim 14, wherein the He flow during active plasmatreatment steps is increased to a rate of about 1500 sccm to about 3000sccm.
 17. The method of claim 14, wherein the O2 during active plasmatreatment step is decreased to a rate of about 50 sccm to 0 sccm. 18.The method of claim 14, wherein the TMS flow during active plasmatreatment step is decreased to a rate of about 100 to 0 sccm.
 19. Themethod of claim 14, wherein the He, TMS and O2 during active plasmatreatment is increased, decreased and decreased respectively withoutchanging the plasma discharge.
 20. The method of claim 14, where a ratioof the low frequency RF power to the total RF power during active plasmatreatment step is substantially the same as during the basic filmforming step which is less than that of 0.5.
 21. The method of claim 14,wherein the pressure during active plasma treatment step issubstantially the same as that during the basic film forming step whichis maintained at a pressure between about 500 Pa to about 800 Pa. 22.The method of claim 14, wherein the silicon carbide layer isoxygen-doped, and wherein the oxygen-doped silicon carbide layer has adielectric constant less than about 3.0.
 23. The method of claim 14,wherein the silicon carbide layer has a leakage current of less than5×10⁻¹⁰ A/cm2 at an electric field of 1 MV/cm.
 24. The method of claim14, wherein the silicon carbide layer is mechanically strong such as hashigh elastic modulus and hardness of approximately >10G Pa and >2G Parespectively when compared to the other low-k films such asfluorosilicate (FSG), hydrogen silisesquioxane (HSQ), methylsilsesquioxane (MSQ), and others like the same.
 25. The method of claim14, where the silicon carbide layer has improved electrical propertiesby the active plasma step, including: i) higher breakdown voltage, ii)lower leakage current and iii) greater film stability.
 26. The method ofclaim 14, wherein the silicon carbide layer minimizes metal diffusionand improves the barrier layer properties.
 27. The method of claim 14,wherein the dielectric constant of the silicon carbide layer in tunable,in that it can be varied as a function of the ratio of the mixedfrequency RF powers.
 28. The method of claim 14, wherein the dielectricconstant of the silicon carbide can be tuned as a function of thecomposition of the gas mixture during film formation.
 29. The methodaccording to claim 14, wherein the film is a copper diffusion barrierlayer.
 30. The method according to claim 14, wherein the film is a low-kfilm.
 31. A method of manufacturing on a semiconductor substrate astructure containing a film in contact with a copper layer, comprisingthe steps of: i) forming a silicon carbide layer on a semiconductorsubstrate by plasma reaction according to a method comprising: (a)providing a silicon source carbon source and oxygen source and an inertgas into a reaction zone including the substrate; (b) applying low andhigh frequency RF energy to the reaction zone thereby depositing asilicon carbide film on the substrate; and (c) continuously activating aplasma in the reaction zone by increasing flow of the inert gas whiledecreasing flow of the silicon source, carbon source and oxygen sourcewhile maintaining the RF energy, thereby reducing a dielectric constantof the silicon carbide film; ii) forming a via in the silicon carbidelayer to expose a portion of the copper layer; iii) forming a trench inthe silicon carbide layer above the via hole, the trench being used toaccommodate a metal wiring; iv) depositing copper in the hole; and v)removing the excess of the copper and resist on top of the siliconcarbide layer.
 32. The method according to claim 31, wherein in step(ii) the hole is produced by forming a resist on top of the siliconcarbide layer and forming a via hole and trench by etching the siliconcarbide layer using the resist, and in step (v) by CMP or the like, theresist and the excess copper are removed so that a surface is exposed.33. The method according to claim 31, wherein steps (i) through (iv) arerepeated at least once.
 34. A method for depositing a silicon carbidelayer onto a substrate, comprising: (a) providing a silicon source,carbon source, and oxygen source, and an inert gas into a reaction zoneincluding the substrate; (b) applying low and high frequency RF energyto the reaction zone, thereby depositing a silicon carbide film on thesubstrate; and (c) continuously activating a plasma in the reaction zoneby increasing flow of the inert gas while decreasing flow of the siliconsource, carbon source, and oxygen source, while maintaining the RFenergy, thereby reducing a dielectric constant of the silicon carbidefilm.